This example is pretty contrived. Normally, I would see this error in acceptance and integration tests, when a component is rendered that calls a service that uses PromiseProxyMixin, or a controller is initialized that uses PromiseProxyMixin, and the test does not need to wait for all promises so it completes and the app is destroyed before the promise resolves.

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Everything is set up in the routes/application. The error is:

<pre><code>

Error: Assertion Failed: calling set on destroyed object

</code></pre>

Open developer tools to see the error. Comment the last line of `beforeModel` to see PromiseProxyMixin work normally.